Rousillon, 16 Barnabas Street, London SW1 (020 7730 5550).Meal for an adult and child, with drinks and service, £90

Shortly after my disappointing meal at the family themed Blue Kangaroo, I was contacted by representatives of Roussillon, a Michelin-starred restaurant in Chelsea. The French chef-proprietor, Alexis Gauthier, had been dismayed to discover that British parents were reluctant to take their children to good restaurants here because they thought they would be unwelcome, I was told. He had therefore created a seven-course 'mini-gastronomes' menu aimed at five to 11 year olds. It is free on the first and third Wednesday lunchtime of every month, a far more generous deal than it sounds: there are many international schools around Roussillon and they have Wednesday afternoons off. However, the menu is also available, by arrangement, at other times for what turns out to be the remarkable price of £15 per child. Accordingly, I booked in for an early dinner one Friday evening with my six-year-old son Eddie, who has expansive tastes. What can I tell you? He's my kid. Picky eating was never really going to be an option.

Roussillon is a handsome rather than pretty red-brick building, with sherbet yellow paintwork outside, and thick carpets and downlighters inside. It is in every way a grown-up place, veering towards the sombre. Food-wise, though, there are light touches, like the dozen or so different breads they brought round, including one studded with chorizo which Eddie liked so much I had to quietly ask the waiters not to pass the basket under his nose too often.

And so to his seven courses, the first of which, a creamy potato soup with a watercress ravioli, was the only misfire. Reasonably enough, I think, the kitchen wanted to start with something soothing and unchallenging. Eddie just thought it dull. He was more excited by the lobster ravioli with a shellfish reduction served to me as an amuse. He scarfed much of that. Most of the courses come with their own drinks, in this case a green tea and honey shot, which also didn't impress. After that, Eddie got into his stride. He loved the glass of pear veloute and the sizeable steamed scallop with summer truffles and a stew of bacon and leeks, which it accompanied. He liked it all so much he didn't let me try any. 'The scallop was really seafoodie,' he said, approvingly. He practically inhaled the tranche of grilled sea bass and the mango that came with it, though was less excited by the ginger and frisee salad or the ginger cordial.

No matter. The meat course was a raging success: a buttery, golden puff pastry shell filled with a stew of long-cooked beef that had broken down into a mass of dark, glossy fibres. This was proper bourgeois cookery which also managed to be extremely accessible. The same is true of everything

I ate from the £48 adult menu: a cep risotto, dressed with veal jus; fillet and belly of pork with a fine crackling; a tiny glazed lemon tart and some lime sorbet to finish. Eddie's first pudding, a rhubarb and pomegranate jelly, was, he said, not sour enough. But the second, an exceptionally well-executed chocolate souffle, practically made him weep with pleasure. 'I want to eat this all the time,' he said. To which I said: 'Dream on, my son.'

On the food side, therefore, Gauthier's venture is a big success: the mini-gastronomes menu is smart and challenging without being scary. There is only one problem, and it is major: the chef has not taken his staff with him on his grand mission. The waiters should have been thrilled to see Eddie there. They should have been eager to talk to any child, desperate to know what they thought of everything. I'm not talking cartwheels and clown suits. They should simply have displayed a genuine interest in having children in the restaurant because that was the whole point of the exercise. Instead they were dour and stiff. They didn't talk to him at all. One of them even huffed when a piece of cutlery went off the table, perhaps for the third time in a two-hour meal. The adult world in which he was a tourist should have looked a truly exciting place that evening; instead it was gloomy. I had noted this lack of enthusiasm when I phoned to book. Not a twinge of excitement that someone was taking them up on the notion, just a monotone at the end of the line like someone's mother had died.

There were other problems with service: a second bottle of water opened without us being asked, for example, or the choice of a wine priced at a hefty £11 a glass without a mention of the cost when I had asked for something to accompany my main course.

At the end, even the kitchen seemed to have lost interest. It sent out a shot glass of 'warm' vanilla milk for Eddie which was so dangerously hot it could have caused severe burns. It was a great disappointment. In short, if this is what Roussillon is like when it's trying to be welcoming to children, God knows what it would be like if it were trying to be hostile.